A perforating device of this type is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 5-138381, for example. The device of this publication includes a source of laser generation. The source of laser generation emits a laser beam continuously. The emitted laser beam is applied to a polygonal mirror in a rotating state. As the polygonal mirror rotates, it cyclically deflects the applied laser beam and converts it into a pulse laser beam. The pulse laser beam is divided into a plurality of beam segments through an optical system, and these beam segments are applied to a tip paper web for use as a web material. While this is done, the tip paper web is traveling, so that the beam segments form a plurality of rows of pores in the tip paper web. Thereafter, the tip paper web is cut to provide a tip paper piece with a given length in a filter attachment, and the tip paper piece is used to connect two cigarettes and a filter plug, whereby a double filter cigarette is manufactured. The double filter cigarette is cut in the center of the tip paper piece, whereupon individual filter cigarettes are obtained.
The perforating device described above has an advantage in being able to form a plurality of rows of pores in the tip paper web by using only the single source of laser generation.
However, the perforating device cannot easily cope with change of the type of the tip paper web. More specifically, the types of tip paper webs used in the manufacture of filter cigarettes, that is, the numbers and positions of rows of pores, vary depending on the brands of the filter cigarettes to be manufactured. The optical system should be changed in order to form tip paper webs with pores that vary in row number and row position. Changing the optical system requires adjustment of paths through which the beam segments are to pass. The replacement of the optical system and the adjustment of the paths. take much labor and time.
More specifically, the optical system of the disclosed perforating device includes a bisecting mirror. The bisecting mirror divides the pulse laser beam into two beam segments, and these beam segments form a row of pores on each of the left- and right-hand side portions of a tip paper web. It is very difficult, however, to make adjustment to guide the beam segments, divided by the bisecting mirror, to the tip paper web with the respective generation cycles and intensities of the beam segments kept equal. Therefore, the pores in each row are subject to variations in size and intervals, so that target air permeability cannot be given accurately to the tip paper web. In consequence, the quality of the filter cigarettes cannot be maintained with high accuracy.